1. Technical Field
The present invention relates to electro-hydraulic forming to contract a tubular member in a die.
2. Background Art
In electro-hydraulic forming (“EHF”), an electric arc discharge is used to convert electrical energy to mechanical energy. A capacitor bank, or other source of stored charge, delivers a high current pulse across two electrodes that are submerged in a fluid, such as oil or water. The electric arc discharge vaporizes some of the surrounding fluid and creates shock waves in the fluid. A workpiece that is in contact with the fluid may be deformed by the shock waves to fill an evacuated die.
Electro-hydraulic forming may be used, for example, to form a flat blank in a one-sided die. The use of EHF for a one-sided die may save tooling costs and may also facilitate forming parts into shapes that are difficult to form by conventional press forming or hydroforming techniques. Electro-hydraulic forming also facilitates forming high strength steel, aluminum and copper alloys. For example, advanced high strength steel (AHSS) and ultra high strength steel (UHSS) can be formed to a greater extent with electro-hydraulic forming techniques when compared to other conventional forming processes. Lightweight materials, such as AHSS and UHSS and high-strength aluminum alloys are lightweight materials that are used to reduce the weight of vehicles.
The use of these high strength, lightweight materials is increasing and has been proposed for hydroforming tubes. Tube hydroforming is well-known technology that is currently used in production. One problem with hydroforming tubes is that the tube tends to thin in areas that are formed to a greater extent.
The above problems are addressed by Applicant's invention as summarized below.